I had to use a proxy and fake a US mailing-address to be allowed to use Spotify (a European service!), from Europe. And I had to try 3-4 times, with different email-addresses, because I had to create new accounts.
This thing took a reasonably seasoned hacker some serious effort to set up. I'm not buying a single device from this company ever again.
Compare that to Chromecasts: You can give those to grandmas and they'll just work.
My guess is if you compare global numbers to US-only numbers you will get very different results, and you will find Roku having almost no marketshare what so ever outside US-borders.